Light emitting device and method of manufacturing the same

ABSTRACT

All lights generated in an organic compound layer are not taken out towards a TFT from a cathode as a transparent electrode. For instance, the light is emitted in a lateral direction (direction parallel to the substrate surface) but the light emitted in the lateral direction is not taken out resultantly, which leads to a loss. Therefore, a light emitting device structured so as to increase the amount of light taken out in a certain direction is provided as well as a method of manufacturing this light emitting device. As a result of etching treatment, an upper edge portion of an insulator ( 19 ) is curved to have a radius of curvature, a slope is formed along the curved face while partially exposing layers ( 18   c  and  18   d ) of a first electrode, and a layer ( 18   b ) of the first electrode is exposed in a region that serves as a light emitting region. Light emitted from an organic compound layer ( 20 ) is reflected by the slope of the first electrode (layers  18   c  and  18   d ) to increase the total amount of light taken out in the direction indicated by the arrow in FIG.  1 A.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a light emitting device with a lightemitting element that emits fluorescent light or phosphorescent lightupon application of electric field to a pair of electrodes of theelement which sandwich a layer containing an organic compound(hereinafter, an organic compound film), and to a method ofmanufacturing the light emitting device. In this specification, the termlight emitting device includes an image display device, a light emittingdevice and a light source (including illuminating device). Also, thefollowing modules are included in the definition of the light emittingdevice: a module obtained by attaching to a light emitting device aconnector such as an FPC (flexible printed circuit; terminal portion), aTAB (tape automated bonding) tape, or a TCP (tape carrier package); amodule in which a printed wiring board is provided at an end of the TABtape or the TCP; and a module in which an IC (integrated circuit) isdirectly mounted to a light emitting element by the COG (chip on glass)system.

2. Description of the Related Art

Light emitting elements, which employ organic compounds as lightemitting member and are characterized by their thinness and lightweight, fast response, and direct current low voltage driving, areexpected to develop into next-generation flat panel displays. Amongdisplay devices, ones having light emitting elements arranged to form amatrix shape are considered to be particularly superior to theconventional liquid crystal display devices for their wide viewing angleand excellent visibility.

It is said that light emitting elements emit light through the followingmechanism: a voltage is applied between a pair of electrodes thatsandwich an organic compound layer, electrons injected from the cathodeand holes injected from the anode are re-combined at the luminescentcenter of the organic compound layer to form molecular excitons, and themolecular excitons return to the base state while releasing energy tocause the light emitting element to emit light. Known as excitationstates are singlet excitation and triplet excitation, and it isconsidered that luminescence can be conducted through either one ofthose excitation states.

Such light emitting devices having light emitting elements arranged toform a matrix can employ passive matrix driving (simple matrix lightemitting devices), active matrix driving (active matrix light emittingdevices), or other driving methods. However, if the pixel density isincreased, active matrix light emitting devices in which each pixel (oreach dot) has a switch are considered as advantageous because they canbe driven with low voltage.

Organic compounds for forming a layer containing an organic compound(strictly speaking, light emitting layer), which is the center of alight emitting element, are classified into low molecular weightmaterials and polymeric (polymer) materials. Both types of materials arebeing studied but polymeric materials are the ones that are attractingattention because they are easier to handle and have higher heatresistance than low molecular weight materials.

The conventional active matrix type light emitting device has thestructure comprising a light emitting element in which an electrodeelectrically connected with TFT on a substrate is formed as an anode, anorganic compound layer is formed thereon, and cathode is formed thereon.And light generated at the organic compound layer can be observed at theTFT side through the anode that is a transparent electrode.

There has been a problem in the structure that an opening ratio isrestricted depending on an arrangement of TFT and wirings in a pixelportion when definition is to be improved.

SUMMARY OF THE INVENTION

Therefore, manufactured in the present invention is an active matrixlight emitting device that has a light emitting element with a structurecalled an upward emission structure. In the upward emission structure, aTFT side electrode which is electrically connected to a TFT on asubstrate serves as an anode, a layer containing an organic compound isformed on the anode, and a cathode that is a transparent electrode isformed on the layer containing an organic compound.

Compared to the downward emission structure, the number of materiallayers through which light emitted from the organic compound-containinglayer passes is smaller in the upward emission structure and stray lightcaused between material layers of different refractive indexes isaccordingly reduced.

Not all of light generated in the organic compound layer are taken outin the direction toward the TFT from the transparent electrode servingas the cathode. For example, light emitted in the lateral direction (thedirection parallel to the substrate face) is not taken out and thereforeis a loss. An object of the present invention is to provide a lightemitting device structured so as to increase the amount of light whichis taken out in a certain direction after emitted from a light emittingelement, as well as a method of manufacturing this light emittingdevice.

A problem of the upward emission structure is that its transparentelectrode has high film resistance. The film resistance becomes evenhigher when the thickness of the transparent electrode is reduced. Whenthe transparent electrode that serves as an anode or a cathode is highin film resistance, a voltage drop makes the intra-plane electricpotential distribution uneven and the luminance becomes fluctuated amonglight emitting elements. Another object of the present invention istherefore to provide a light emitting device structured so as to lowerthe film resistance of a transparent electrode in a light emittingelement, as well as a method of manufacturing the light emitting device.Still another object of the present invention is to provide an electricappliance that uses this light emitting device as its display unit.

In the present invention, a first electrode is formed from a laminate ofmetal layers and the edge of the first electrode is covered with aninsulator (also called as a bank or a partition wall). Using theinsulator as a mask, the center of the first electrode is etched in aself-aligning manner so that the center is thinned and a leveldifference is formed in the edge while a part of the insulator is alsoetched. As a result of this etching, the center of the first electrodeobtains a thin, flat surface and the edge of the first electrode that iscovered with the insulator becomes thicker than the center, therebygiving the first electrode a concave shape. On the first electrode, alayer containing an organic compound and a second electrode are formedto complete a light emitting element.

The present invention is for increasing the amount of light taken out ina certain direction (a direction in which light passes the secondelectrode) by reflecting or collecting light emitted in the lateraldirection at the slope formed in the stepped portion of the firstelectrode.

Accordingly, a portion to form the slope is preferably made from a metalthat reflects light, for example, a material mainly containing aluminumor silver, whereas the center portion that is in contact with theorganic compound-containing layer is formed from an anode materialhaving a large work function or a cathode material having a small workfunction.

Structure 1 of the present invention disclosed herein is a lightemitting device comprising:

a first electrode connected to a thin film transistor on a substratethat has an insulating surface;

an insulator covering the edge of the first electrode;

a layer which contains an organic compound and which is in contact withthe top face of the first electrode; and

a second electrode that is in contact with the top face of the layer,

characterized in that the first electrode is sloped from its edge towardits center to have a slope and that the slope reflects light emittedfrom the organic compound-containing layer.

Structure 2 of the present invention is a light emitting devicecomprising:

a first electrode connected to a thin film transistor on a substratethat has an insulating surface;

an insulator covering the edge of the first electrode;

a layer which contains an organic compound and which is in contact withthe top face of the first electrode; and

a second electrode that is in contact with the top face of the layer,

characterized in that the first electrode is thinner in the center thanin the edge to form a concave shape.

Structure 3 of the present invention is a light emitting devicecomprising:

a first electrode connected to a thin film transistor on a substratethat has an insulating surface;

an insulator covering the edge of the first electrode;

a layer which contains an organic compound and which is in contact withthe top face of the first electrode; and

a second electrode that is in contact with the top face of the layer,

characterized in that the first electrode has a multi-layer structureand that the number of layers is larger in the edge than in the center.

The present invention gives an insulator placed between pixels (calledas a bank, a partition wall, a barrier or the like) a particular shapeto avoid insufficient coverage when forming by application a highmolecular weight organic compound film. The above structures arecharacterized in that an upper edge portion of the insulator is curvedto have a radius of curvature and that the radius of curvature is set to0.2 to 3 μm. The taper angle of the insulator is set to 35 to 55°.

By giving the edge the radius of curvature, the level difference is wellcovered and the organic compound-containing layer and other films formedon the insulator can be made very thin.

The above structures are characterized in that the first electrode issloped toward its center and that the angle of inclination (also calledas a taper angle) of the slope is more than 30° and less than 70°,preferably, less than 60°. The angle of inclination, the material andthickness of the organic compound layer, and the material and thicknessof the second electrode have to be set suitably to prevent lightreflected by the slope of the first electrode from scattering orstraying between layers.

The above structures are characterized in that the second electrode is aconductive film transmissive of light, for example, a thin metal film ora transparent conductive film.

The above structures are characterized in that the first electrode has aconcave shape and is formed in a self-aligning manner using theinsulator as a mask. Accordingly, there is no need for a new mask toform the first electrode shape. The stepped portion (the upper edgeportion of the slope portion) of the first electrode is almost flushwith a side face of the insulator and, in order to cover the leveldifference well, it is preferable for the slope of the first electrodeand the side face of the insulator to have the same angle ofinclination.

The above structures are characterized in that the first electrode is ananode whereas the second electrode is a cathode. Alternatively, theabove structures are characterized in that the first electrode is acathode whereas the second electrode is an anode.

The light emitting device in each of the above structures ischaracterized in that the organic compound-containing layer is formedfrom a material that emits white light and that the layer is used incombination with color filters provided in a sealing member.Alternatively, the light emitting device in each of the above structuresis characterized in that the organic compound-containing layer is formedfrom a material that emits light of a single color and that the layer isused in combination with color conversion layers or colored layersprovided in a sealing member.

In the present invention, after the level difference in the firstelectrode is formed, a wire (also called as an auxiliary wire or a thirdelectrode) may be formed by evaporation using an evaporation mask on theinsulator placed between pixel electrodes in order to reduce the filmresistance of the electrode that serves as a cathode (the electrode thattransmits light). The present invention is also characterized in thatthe auxiliary wire is used to form a lead-out wire to obtain connectionwith other wires in layers below.

A structure of the present invention for obtaining Structures 1, 2, and3 is a method of manufacturing a light emitting device with a lightemitting element having an anode, a layer containing an organiccompound, and a cathode, the organic compound-containing layer being incontact with the anode, the cathode being in contact with the organiccompound-containing layer, characterized by comprising:

a step of forming an insulator to cover the edge of a first electrodethat is a laminate of metal layers;

a step of thinning the center of the first electrode so as to expose aslope along the edge of the first electrode by etching using theinsulator as a mask;

a step of forming the organic compound-containing film; and

a step of forming a second electrode on the organic compound-containingfilm from a thin metal film that transmits light.

The above structure related to a manufacturing method is characterizedin that the first electrode is a laminate of a metal layer reflectinglight and a metal layer serving as an etching stopper and that the metallayer reflecting light is etched to expose a metal material thatreflects light in the slope.

As a result of the etching of the first electrode, a surface of themetal layer serving as an etching stopper may be etched slightly.

The above structure related to a manufacturing method is characterizedin that the first electrode is an anode and is formed from a metal layerthat is larger in work function than the second electrode.

The above structure related to a manufacturing method is characterizedin that the first electrode is a laminate of a first metal layercontaining titanium, a second metal layer containing titanium nitride ortungsten nitride, a third metal layer containing aluminum, and a fourthmetal layer containing titanium nitride.

For the first metal layer, a metal material having satisfactory ohmiccontact with silicon (typically titanium) is suitable because the firstmetal layer is in contact with a source region or drain region of a TFT.A material having a large work function is preferred for the secondmetal layer which functions as an anode. For the third metal layer whichreflects light of a light emitting element, a metal material having highlight reflectance is preferred. A metal material which can preventhillock and whisker of the third metal layer and which can avoidspecular reflection of the third metal layer (titanium nitride ortitanium) is preferred for the fourth metal layer.

The first electrode is not limited to the above four-layer structure butmay have any laminate structure as long as it includes two layers ormore, that is, at least a metal layer to function as an anode and ametal layer that has a slope for reflecting light of a light emittingelement.

FIG. 12 shows the reflectance of an aluminum film containing a minuteamount of Ti and the reflectance of a TiN film (100 nm). Titaniumnitride is a material that can prevent specular reflection. Whentitanium nitride is used for an anode, almost no light is reflected andtherefore interference by return light of a light emitting element doesnot take place. Accordingly, the device can have a panel structure thatdoes not need a circular polarizing plate.

For example, the first electrode may have a six-layer structure with thefirst metal layer being a titanium film, the second metal layer being atitanium nitride film, the third metal layer being analuminum-containing metal film, the fourth metal layer being a titaniumnitride film, the fifth metal layer being an aluminum-containing metalfilm, and the sixth metal layer being a titanium nitride film. In thissixth-layer structure, the fourth metal layer serves as an anode and thefifth metal layer reflects light from a light emitting element at itsslope. Since the aluminum-containing metal film is provided under theanode, the resistance of the entire first electrode can be lowered. Thissix-layer structure is particularly effective for a light emittingdisplay device in which the area per pixel (light emitting region) islarge or which has a large screen.

In the above structure related to a manufacturing method, the workfunction of the metal layer that serves as an anode may be raised byultraviolet ray irradiation treatment in an ozone atmosphere (called asUV-ozone treatment). FIG. 13 shows results of measuring changes in workfunction with UV-ozone treatment time. As shown in FIG. 13, the initialwork function of titanium nitride, 4.7 eV, is raised by UV treatment(for six minutes) to 5.05 eV. Note that, similarly, the work function oftantalum nitride shows an increase. In the above structure related to amanufacturing method, the work function of the metal layer that servesas an anode may be raised by plasma treatment using one or more kinds ofgas selected from the group consisting of N₂, O₂, Ar, BCl, and Cl₂.

In FIG. 13, the work function is measured in an atmospheric air byphotoelectron spectroscopy using “Photoelectron Spectroscope AC-2”, aproduct of RIKEN KEIKI Co., Ltd.

If plasma etching is employed in the step of thinning the center of thefirst electrode so as to expose a slope along the edge of the firstelectrode by etching using the insulator as a mask, some etching gas iscapable of increasing the work function of the metal layer that servesas an anode at the same time the center is thinned.

The above structure related to a manufacturing method is characterizedin that an upper edge portion of the insulator for covering the edgeportion of the first electrode is curved to have a radius of curvatureand that the radius of curvature is set to 0.2 to 3 μm.

An EL element has a layer containing an organic compound that providesluminescence upon application of electric field (electroluminescence)(hereinafter referred to as EL layer), in addition to ananode and a cathode. Luminescence obtained from organic compounds isdivided into light emission upon return to the base state from singletexcitation (fluorescence) and light emission upon return to the basestate from triplet excitation (phosphorescence). Both types of lightemission can be employed in a light emitting device manufactured inaccordance with the present invention.

A light emitting element having an EL layer (EL element) is structuredso as to sandwich the EL layer between a pair of electrodes. Usually,the EL layer has a laminate structure. A typical example of the laminatestructure is one consisting of a hole transporting layer, a lightemitting layer, and an electron transporting layer. This structure hasvery high light emission efficiency and is employed in most of lightemitting devices that are currently under development.

Other examples of the laminate structure include one in which a holeinjection layer, a hole transporting layer, a light emitting layer, andan electron transporting layer are layered on an anode in this order,and one in which a hole injection layer, a hole transporting layer, alight emitting layer, an electron transporting layer, and an electroninjection layer are layered on an anode in this order. The lightemitting layer may be doped with a fluorescent pigment or the like.These layers may all be formed of low molecular weight materials or mayall be formed of high molecular weight materials. In this specification,all layers placed between an anode and a cathode together make an ELlayer. Accordingly, the above hole injection layer, hole transportinglayer, light emitting layer, electron transporting layer, and electroninjection layer are included in an EL layer.

In a light emitting device of the present invention, how screen displayis driven is not particularly limited. For example, a dot-sequentialdriving method, a linear-sequential driving method, a plane-sequentialdriving method or the like can be employed. Typically, alinear-sequential driving method is employed and a time ratio gray scaledriving method or an area ratio gray scale driving method is chosensuitably. A video signal inputted to a source line of the light emittingdevice may be an analog signal or a digital signal, and driving circuitsand other circuits are designed in accordance with the type of the videosignal as appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A and 1B are diagrams showing Embodiment Mode 1;

FIGS. 2A and 2B are diagrams showing Embodiment 1;

FIGS. 3A to 3C are diagrams showing Embodiment 1;

FIGS. 4A to 4C are diagrams showing Embodiment Mode 3;

FIGS. 5A to 5C are diagrams showing Embodiment Mode 2;

FIGS. 6A and 6B are diagrams showing Embodiment 2;

FIG. 7 is a diagram showing Embodiment 2;

FIG. 8 is a diagram showing Embodiment 2;

FIGS. 9A and 9B are diagrams showing Embodiment 3;

FIGS. 10A to 10F are diagrams showing examples of electronic equipment;

FIGS. 11A to 11C are diagrams showing examples of electronic equipment;

FIG. 12 is a graph showing the reflectance of an aluminum film thatcontains a minute amount of Ti and the reflectance of a TiN film (100nm); and

FIG. 13 is a graph showing changes in work function with UV-ozonetreatment time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment Modes of the present invention will be described below.

Embodiment Mode 1

FIG. 1A is a sectional view of an active matrix light emitting device (apart of one pixel). Described here as an example is a light emittingelement which uses as its light emitting layer an organiccompound-containing layer formed of a high molecular weight materialthat emits white light.

In FIG. 1A, a TFT (p-channel TFT) on a substrate 10 having an insulatingsurface is an element for controlling a current flowing into an EL layer20 that emits white light. Of regions denoted by 13 and 14, one is asource region and the other is a drain region. A base insulating film 11(here a laminate of an insulating nitride film as a lower layer and aninsulating oxide film as an upper layer) is formed on the substrate 10.A gate insulating film 12 is placed between a gate electrode 15 and anactive layer of the TFT. Denoted by 16 a is an interlayer insulatingfilm formed of an organic material or an inorganic material. Referencesymbol 16 b represents a protective film formed of silicon nitride,silicon nitroxide, aluminum nitride, or aluminum nitroxide. Although notshown in the drawing, one pixel has another or more TFTs (n-channel TFTsor p-channel TFTs) other than this TFT. The TFT here has one channelformation region. However, the number of channel formation regions isnot particularly limited, and the TFT may have more than one channels.

Reference symbols 18 a to 18 d denote layers of a first electrode,namely, an anode (or cathode) of the organic light emitting elementwhereas a second electrode formed from a conductive film, namely, acathode (or anode) of the organic light emitting element is denoted, by21. Here, reference symbol 18 a is a titanium film, 18 b is a titaniumnitride film, 18 c is a film mainly containing aluminum, and 18 d is atitanium nitride film. The films are layered in order and 18 b that isin contact with the organic compound-containing layer 20 functions asthe anode. A power supplying line 17 is formed to have the same laminatestructure. Since the above laminate structure includes a film mainlycontaining aluminum, a low-resistant wire is obtained and a source wire22 and others are formed at the same time.

To make the organic compound-containing layer 20 emit white light, anaqueous solution of poly(ethylene dioxythiophene)/poly(styrene sulfonicacid) (PEDOT/PSS) is applied to the entire surface and baked to form afilm that works as a hole injection layer. Then, a polyvinyl carbazole(PVK) solution doped with a luminescence center pigment (such as1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1),Nile red, or coumarin 6) is applied to the entire surface and baked toform a film that works as a light emitting layer. The solvent ofPEDOT/PSS is water and PEDOT/PSS is not dissolved in an organic solvent.Accordingly, the hole injection layer does not go back to the meltedstate when PVK is applied thereon. Since PEDOT/PSS and PVK havedifferent solvents, they are preferably formed into films in differentfilm forming chambers. The organic compound-containing layer 20 mayinstead be a single layer. In this case, a 1,3, 4-oxadiazole derivative(PBD) capable of transporting electrons is dispersed in polyvinylcarbazole (PVK) capable of transporting holes. Another method to obtainwhite light emission is to disperse 30 wt % of PBD as an electrontransporting agent and disperse four kinds of pigments (TPB, coumarin 6,DCM1, and Nile red) in appropriate amounts.

Alternatively, a combination of films is chosen appropriately from afilm containing an organic compound that emits red light, a filmcontaining an organic compound that emits green light, and a filmcontaining an organic compound that emits blue light to overlap eachother and mix their colors, thereby obtaining white light emission.

For the second electrode 21, a CaF₂ film is formed by evaporation tohave a thickness of 1 to 10 nm and then an Al film is formed bysputtering or evaporation to have a thickness of about 10 nm to functionas the cathode. The material and thickness of the cathode have to bechosen suitably to transmit light from the organic compound-containinglayer 20. In this specification, the term cathode includes not only asingle layer of a material having a small work function but also alaminate of a thin film of a small work function material and aconductive film.

Using an Al film as the second electrode 21 means that a material thatis not an oxide comes into contact with the organic compound-containinglayer 20. As a result, the reliability of the light emitting device isimproved. Instead of an Al film, a transparent conductive film (such asan ITO (indium oxide-tin oxide alloy) film, an In₂O₃—ZnO (indiumoxide-zing oxide alloy) film, or a ZnO (zinc oxide) film) may beemployed as the second electrode 21. The CaF₂ layer may be replaced by athin metal layer (typically a film of such alloy as MgAg, MgIn, orAlLi).

Both end portions of the first electrode 18 and in-between areas arecovered with an insulator 19 (also called as a barrier or a bank). Inthe present invention, what sectional shape the insulator 19 takes isimportant. The insulator 19 is formed by etching treatment, throughwhich the concave shape of the first electrode 18 is obtained. If anupper edge portion of the insulator 19 is not curved, a film formationdefect is likely to occur and an unwanted convex portion is formed onthe upper edge of the insulator 19. Therefore, the present inventionuses etching treatment to make an upper edge portion of the insulator 19curved to have a radius of curvature, to form a slope along the curvedface partially exposing the layers 18 c and 18 d of the first electrode,and to expose the layer 18 b of the first electrode in a region thatserves as a light emitting region. The exposed surface of the layer 18 bof the first electrode may be leveled by CMP or other treatment. Theradius of curvature is preferably set to 0.2 to 3 μm. The presentinvention can give the organic compound film and the metal filmexcellent coverage. The taper angle in the side face of the insulator 19is equal to the taper angle in the slope of the layers 18 c and 18 d ofthe first electrode, and is set to 45°±10°.

For instance, when the insulator 19 is formed of positive acrylic resin,the layer 18 a of the first electrode is a 60 nm thick Ti film, thelayer 18 b of the first electrode is a 100 nm thick TiN film, the layer18 c of the first electrode is a 350 nm thick Al—Ti film, and the layer18 d of the first electrode is a 100 nm thick Ti film, etchingconditions include employing ICP etching apparatus, using as reactiongas BCl₃ and Cl₂ at a ratio of 60 (sccm):20 (sccm), and giving an RF(13.56 MHz) power of 450 W to a coiled electrode at a pressure of 1.9Pa. At the same time, the substrate side (sample stage) is also given anRF (13.56 MHz) power of 100 W for dry etching. After the Al—Ti layer(the layer 18 c of the first electrode) is etched, the TiN layer (thelayer 18 b of the first electrode) is exposed by over-etching for 15seconds.

The present invention is characterized in that light emitted from theorganic compound layer 20 is reflected at the slope of the layers 18 cand 18 d of the first electrode to increase the total amount of lighttaken out in the direction indicated by the arrow in FIG. 1A.

As shown in FIG. 1B, an auxiliary electrode 23 may be provided on theconductive film 21 in order to lower the resistance of the conductivefilm (cathode) 21. The auxiliary electrode 23 is selectively formed byevaporation using an evaporation mask.

Although not shown in the drawing, a protective film is preferablyformed on the second electrode 21 in order to enhance the reliability ofthe light emitting device. This protective film is an insulating filmwhich mainly contains silicon nitride or silicon nitroxide and which isformed by sputtering (the DC method or the RF method), or a thin filmmainly containing carbon. A silicon nitride film can be formed in anatmosphere containing nitrogen and argon using a silicon target. Asilicon nitride target may be employed instead. The protective film mayalso be formed by film forming apparatus that uses remote plasma. Theprotective film is made as thin as possible to allow emitted light topass through the protective film.

The present invention is characterized in that the thin film mainlycontaining carbon is a DLC (diamond-like carbon) film with a thicknessof 3 to 50 nm. In viewpoint of short-range order, a DLC film has Sp³bonds as bonds between carbons. Macroscopically, a DLC film has anamorphous structure. 70 to 95 atomic % carbon and 5 to 30 atomic %hydrogen constitute a DLC film, giving the film high degree of hardnessand excellent insulating ability. Such DLC film is characteristicallylow in transmittance of gas such as steam and oxygen. Also, it is knownthat the hardness of a DLC film is 15 to 25 GPa according to measurementby a microhardness tester.

A DLC film is formed by plasma CVD (typically, RF plasma CVD, microwaveCVD, or electron cyclotron resonance (ECR) CVD) or sputtering. Any ofthe film formation methods can provide a DLC film with excellentadhesion. In forming a DLC film, the substrate is set as a cathode.Alternatively, a dense and hard DLC film is formed by applying negativebias and utilizing ion bombardment to a certain degree.

Reaction gas used to form the film are hydrogen gas and hydrocarbon-based gas (for example, CH₄, C₂H₂, or C₆H₆) and are ionized byglow discharge. The ions are accelerated to collide against the cathodeto which negative self-bias is applied. In this way, a dense, flat, andsmooth DLC film is obtained. The DLC film is an insulating filmtransparent or translucent to visible light.

In this specification, being transparent to visible light means having avisible light transmittance of 80 to 100% whereas being translucent tovisible light means having a visible light transmittance of 50 to 80%.

The description given here takes a top gate TFT as an example. However,the present invention is applicable to any TFT structure. For instance,the invention can be applied to a bottom gate (reverse stagger) TFT anda forward stagger TFT.

Embodiment Mode 2

A method of combining a white color luminescent element and a colorfilter (hereinafter, referred to as color filter method) will beexplained in reference to FIG. 5A as follows.

The color filter method is a system of forming a light emitting elementhaving an organic compound film displaying white color luminescence andpassing the provided white color luminescence through a color filter tothereby achieve luminescence of red, green, and blue.

Although there are various methods of achieving white colorluminescence, a case of using a luminescent layer comprising a highmolecular material formable by coating will be explained here. In thiscase, doping of a color pigment to the high molecular material forconstituting a luminescent layer can be carried out by preparing asolution and can extremely easily be achieved in comparison with a vapordeposition method for carrying out common vapor deposition for doping aplurality of color pigments.

Specifically, after coating and baking an aqueous solution of poly(ethylenedioxythiophene)/poly (stylenesulfonic acid) (PEDOT/PSS)operated as a hole injecting layer over an entire face of an anodecomprising a metal having large work function (Pt, Cr, W, Ni, Zn, Sn,In), thereafter coating and baking a polyvinyl carbazole (PVK) solutiondoped with a luminescent core pigment (1,1,4,4-tetraphenyl 1,3-butadience (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran(DCM1),Nile red, coumarin 6 or the like) operating as the luminescent layerover the entire face, a cathode comprising a laminated layer of a thinfilm including metal having small work function (Li, Mg, Cs) and atransparent conductive film (ITO (indium oxide tin oxide alloy), indiumoxide zinc oxide alloy (In₂O₃—ZnO), zinc oxide (ZnO) or the like)laminated thereabove is formed. Further, PEDOT/PSS uses water as asolvent and is not dissolved in an organic solvent. Therefore, even whenPVK is coated thereabove, there is no concern of dissolving again.Further, kinds of solvents of PEDOT/PSS and PVK differ from each otherand therefore, it is preferable that the same film forming chamber isnot used therefor.

Further, although an example of laminating organic compound layers isshown in the above-described example, a single layer of an organiccompound layer can be constituted. For example, 1,3,4-oxadiazolederivative (PBD) having electron transporting performance may bedispersed in polyvinyl carbazole (PVK) having hole transportingperformance. Further, white color luminescence is achieved by dispersing30 wt % of PBD as an electron transporting agent and dispersingpertinent amounts of four kinds of color pigments (TPB, coumarin 6,DCM1, Nile red).

Further, the organic compound film is formed between the anode and thecathode and by recombining holes injected from the anode and electronsinjected from the cathode at the organic compound film, white colorluminescence is achieved in the organic compound film.

Further, it is also possible to achieve white color luminescence as awhole by pertinently selecting an organic compound film for carrying outred color luminescence, an organic compound film for carrying out greencolor luminescence, and an organic compound film for carrying out bluecolor luminescence, and laminating the films to mix color.

The organic compound film formed as described above can achieve whitecolor luminescence as a whole.

By forming color filters respectively provided with the coloring layer(R) for absorbing other than red color luminescence, a coloring layer(G) for absorbing other than green color luminescence and the coloringlayer (B) for absorbing other than blue color luminescence in adirection of carrying out white color luminescence by the organiccompound film, white color luminescence from the light emitting elementcan respectively be separated to achieve red color luminescence, greencolor luminescence and blue color luminescence. Further, in the case ofan active matrix type, a structure in which TFT is formed between thesubstrate and the color filter is constituted.

Further, starting from simplest stripe pattern, skewed mosaic alignment,triangular mosaic alignment, RGBG four pixels alignment or RGBW fourpixels alignment can be used for the coloring layer (R, G, B).

A coloring layer for constituting a color filter is formed by using acolor resist comprising an organic photosensitive material dispersedwith a pigment. Further, chromaticity coordinates of white colorluminescence are (x, y)=(0.34, 0.35). It is known that color reproducingperformance as full color is sufficiently ensured.

Further, in this case, even when achieved luminescent color differs, theconstitution is formed with all the organic compound films displayingwhite color luminescence and therefore, it is not necessary to form theorganic compound film to coat to divide for each luminescent color.Further, a polarizer for a circularly polarized light for preventingmirror reflection is not particularly needed.

Next, a CCM (color changing mediums) method realized by combining a bluecolor light emitting element having a blue color luminescent organiccompound film and a fluorescent color changing layer will be explainedin reference to FIG. 5B.

According to the CCM method, the fluorescent color changing layer isexcited by blue color luminescence emitted from the blue colorluminescent element and color is changed by each color changing layer.Specifically, changing from blue color to red color by the colorchanging layer (B→R), changing from blue color to green color by thecolor changing layer (B→G) and changing from blue color to blue color bythe color changing layer (B→B) (further, changing from blue color toblue color may not be carried out) are carried out to achieve red color,green color and blue color luminescence. Also in the case of the CCMmethod, the structure in which TFT is formed between the substrate andthe color changing layer is constituted in the case of the active matrixtype.

Further, also in this case, it is not necessary to form the organiccompound films to coat to divide also in this case. Further, a polarizerfor a circularly polarized light for preventing mirror reflection is notparticularly needed.

Further, when the CCM method is used, since the color changing layer isfluorescent, the color changing layer is excited by external light and aproblem of reducing contrast is posed and therefore, as shown by FIG.5C, the contrast may be made conspicuous by mounting color filters.

Further, this embodiment mode can be combined with Embodiment Mode 1.

Embodiment Mode 3

Here, a total of an EL module and arrangement of a drying agent will beexplained in reference to FIG. 4. FIG. 4A is a top view of the ELmodule. FIG. 4B is a part of a cross-sectional view.

A substrate provided with numerous TFTs (also referred to as TFTsubstrate) is provided with a pixel portion 40 for display, drivercircuits 41 a and 41 b for driving respective pixels of the pixelportion, a connecting portion for connecting the electrode provided overthe EL layer and an extended wiring, a terminal portion 42 for pastingFPC for connecting to outside circuit and a drying agent 44. Further,the drying agent may be arranged such that a total of the drivercircuits is concealed by the drying agent as shown by FIG. 4C althoughthe drying agent is arranged to overlap a portion thereof in FIG. 4A andFIG. 4B. Further, the constitution is hermetically sealed by thesubstrate for sealing the EL element and a seal member 49. Further, FIG.4B is a sectional view when the constitution is cut by a chain line B–B′in FIG. 4A.

Pixels are numerously arranged regularly at the pixel portion 40 andarranged in an order of R, G, B in X direction although not illustratedhere.

Further, as shown by FIG. 4B, the seal substrate 48 is pasted by theseal member 49 to maintain an interval of about 2 through 30 μm and allof the light emitting elements are hermetically sealed. A recessedportion is formed at the seal substrate 48 by sand blast method or thelike and the recessed portion is arranged with the drying agent.Further, the seal member 49 is preferably constituted by a narrow frameformation to overlap a portion of the driver circuits. Degassing ispreferably carried out by carrying out annealing in vacuum immediatelybefore pasting the seal substrate 48 by the seal member 49. Further,when the seal substrate 48 is pasted, the pasting is preferably carriedout under an atmosphere including an inert gas (rare gas or nitrogen).

Further, this embodiment mode can freely be combined with EmbodimentMode 1 or Embodiment Mode 2.

The present invention is described in more detail with the followingEmbodiments.

Embodiment 1

In this embodiment, a brief description is given with reference to FIGS.2A to 3C on an example of procedure of forming a light emitting elementin accordance with the present invention.

First, a base insulating film 31 is formed on a substrate 30 which hasan insulating surface.

The base insulating film 31 is a laminate and the first layer is asilicon oxynitride film formed to have a thickness of 10 to 200 nm(preferably 50 to 100 nm) by plasma CVD using as reaction gas SiH₄, NH₃,and N₂O. Here, a silicon oxynitride film (composition ratio: Si=32%,O=27%, N=24%, H=17%) with a thickness of 50 nm is formed. The secondlayer of the base insulating film is a silicon oxynitride film formed tohave a thickness of 50 to 200 nm (preferably 100 to 150 nm) by plasmaCVD using as reaction gas SiH₄ and N₂O. Here, a silicon oxynitride film(composition ratio: Si=32%, O=59%, N=7%, H=2%) with a thickness of 100nm is formed. Although the base insulating film 31 in this embodimenthas a two-layer structure, a single layer or a laminate of more than twolayers of the above insulating films may be employed instead.

Next, a semiconductor layer is formed on the base film. Thesemiconductor layer to serve as an active layer of the TFT is obtainedby forming a semiconductor film that has an amorphous structure througha known method (sputtering, LPCVD, plasma CVD, or the like), subjectingthe film to known crystallization treatment (laser crystallization,thermal crystallization, thermal crystallization using nickel or othercatalysts, or the like), and then patterning the obtained crystallinesemiconductor film into a desired shape. The thickness of thesemiconductor layer is set to 25 to 80 nm (preferably 30 to 60 nm). Thematerial of the crystalline semiconductor film is not limited butpreferably is silicon, a silicon germanium alloy, or the like.

When laser crystallization is employed to form the crystallinesemiconductor film, a pulse oscillation type or continuous wave excimerlayer, YAG layer, or YVO₄ laser is used. Laser light emitted from one ofsuch laser oscillators is collected by an optical system into a linearshape before irradiating the semiconductor film. Crystallizationconditions are chosen to suit individual cases. However, when an excimerlayer is employed, the pulse oscillation frequency is set to 30 Hz andthe laser energy density is set to 100 to 400 mJ/cm² (typically 200 to300 mJ/cm²). When a YAG laser is employed, the second harmonic thereofis used, the pulse oscillation frequency is set to 1 to 10 kHz, and thelaser energy density is set to 300 to 600 mJ/cm² (typically 350 to 500mJ/cm²). The laser light is collected to have a width of 100 to 1000 μm,for example, 400 μm, into a linear shape and the entire surface of thesubstrate is irradiated with this linear laser light setting the laserlight overlap ratio to 80 to 98%.

Next, the surface of the semiconductor layer is washed with an etchantcontaining hydrofluoric acid to form a gate insulating film 33 thatcovers the semiconductor layer. The gate insulating film 33 is aninsulating film containing silicon and is formed by plasma CVD orsputtering to have a thickness of 40 to 150 nm. In this embodiment, asilicon oxynitride film (composition ratio: Si=32%, O=59%, N=7%, H=2%)is formed by plasma CVD to have a thickness of 115 nm. The gateinsulating film is not limited to the silicon oxynitride film, ofcourse, but may be a single layer or laminate of other insulating filmsthat contain silicon.

The surface of the gate insulating film 33 is washed and then a gateelectrode is formed.

Next, the semiconductor layer is appropriately doped with an impurityelement that imparts a semiconductor the p type conductivity, here,boron (B), to form a source region 32 and a drain region 32. After thedoping, the semiconductor layer is subjected to heat treatment,irradiation of intense light, or laser light irradiation in order toactivate the impurity element. At the same time the impurity element isactivated, plasma damage to the gate insulating film and plasma damageto the interface between the gate insulating film and the semiconductorlayer are repaired. It is particularly effective to activate theimpurity element by irradiating the substrate from the front or backwith the second harmonic of a YAG laser at room temperature to 300° C. AYAG laser is a preferable activation measure because it requires littlemaintenance.

The subsequent steps include forming an interlayer insulating film 35from an organic or inorganic material (an applied silicon oxide film,PSG (phosphorus-doped glass), BPSG (glass doped with boron andphosphorus), or the like), hydrogenating the semiconductor layer, andforming contact holes reaching the source region or drain region. Then,a source electrode (wire) and a first electrode (drain electrode) 36 areformed to complete the TFT (p-channel TFT).

Although the description in this embodiment uses a p-channel TFT, ann-channel TFT can be formed if an n type impurity element (such as P orAs) is used instead of a p type impurity element.

The description given in this embodiment takes a top gate TFT as anexample. However, the present invention is applicable to any TFTstructure. For instance, the invention can be applied to a bottom gate(reverse stagger) TFT and a forward stagger TFT.

Formed through the above steps are the TFT (only the drain region 32 isshown in the drawing), the gate insulating film 33, the interlayerinsulating film 35, and layers 36 a to 36 d of the first electrode (FIG.3A).

The layers 36 a to 36 d of the first electrode in this embodiment areeach a film mainly containing an element selected from the groupconsisting of Ti, TiN, TiSi_(x)N_(y), Al, Ag, Ni, W, WSi_(x), WN_(x),WSi_(x)N_(y), Ta, TaN_(x), TaSi_(x)N_(y), NbN, MoN, Cr, Pt, Zn, Sn, In,and Mo, or a film mainly containing an alloy or compound material of theabove elements, or a laminate of these films. The total thickness of thelayers 36 a to 36 d is set between 100 nm and 800 nm.

Particularly, the layer 36 a of the first electrode that comes intocontact with the drain region 32 is preferably formed of a material thatcan form an ohmic contact with silicon, typically titanium, and is givena thickness of 10 to 100 nm. For the layer 36 b of the first electrode,a material that has a large work function when formed into a thin film(TiN, TaN, MoN, Pt, Cr, W, Ni, Zn, Sn) is preferred, and the thicknessof the layer is set to 10 to 100 nm. For the layer 36 c of the firstelectrode, a metal material reflective of light, typically, a metalmaterial mainly containing Al or Ag, is preferred, and the thickness ofthe layer is set to 100 to 600 nm. The layer 36 b of the first electrodealso functions as a blocking layer for preventing the layers 36 c and 36a of the first electrode from forming an alloy. For the layer 36 d ofthe first electrode, a material capable of preventing oxidation andcorrosion of the layer 36 c of the first electrode and avoiding hillockor the like is preferred (typically a metal nitride such as TiN or WN),and the thickness of the layer is set to 20 to 100 nm.

The layers 36 a to 36 d of the first electrode can be formed at the sametime other wires, for example, a source wire 34 and a power supplyingline, are formed. Accordingly, the process needs fewer photomasks (sevenmasks in total: a patterning mask for the semiconductor layer (Mask 1),a patterning mask for the gate wire (Mask 2), a doping mask forselective doping by an n type impurity element (Mask 3), a doping maskfor selective doping by a p type impurity element (Mask 4), a mask forforming contact holes that reach the semiconductor layer (Mask 5), apatterning mask for the first electrode, the source wire, and the powersupplying line (Mask 6), and a mask for forming an insulator (Mask 7)).In prior art, the first electrode is formed on a layer different fromthe one where the source wire and the power supplying line are formedand therefore a mask for forming the first electrode alone is needed,thus making the number of masks required 8 in total. When the layers 36a to 36 d of the first electrode and the wires are formed at the sametime, it is desirable to set the total wire electric resistance low.

Next, the insulator (called as a bank, a partition wall, a barrier, orthe like) is formed to cover the edge of the first electrode (and aportion that is in contact with the drain region 32) (FIG. 3B). Theinsulator is a film or a laminate of inorganic materials (such assilicon oxide, silicon nitride, and silicon oxynitride) andphotosensitive or non-photosensitive organic materials (such aspolyimide, acrylic, polyamide, polyimideamide, resist, andbenzocyclobutene). Photosensitive organic resin is used in thisembodiment. If positive photosensitive acrylic is used as a material ofthe insulator, for example, it is preferable to curve only an upper edgeportion of the insulator to give a radius of curvature. A negativephotosensitive material which becomes insoluble in an etchant underlight and a positive photosensitive material which becomes soluble in anetchant under light both can be used for the insulator.

The insulator is etched as shown in FIG. 3C and, simultaneously, thelayers 36 c and 36 d of the first electrode are partially removed. It isimportant to etch the films such that a slope is formed in the exposedface of the layer 36 c of the first electrode and the layer 36 b of thefirst electrode obtains a flat exposed face. This etching uses dryetching or wet etching, and is finished in one step or divided intoseveral steps. Etching conditions that make the selective ratio betweenthe layer 36 b of the first electrode and the layer 36 c of the firstelectrode high are chosen. Preferably, the final radius of curvature ofthe upper edge portion of the insulator is 0.2 to 3 μm. The final angleof the slope descending toward the center of the first electrode (theangle of inclination or taper angle) is more than 30° and less than 70°,so that the slope reflects light emitted from an organiccompound-containing layer which is formed later.

Next, an organic compound-containing layer 38 is formed by evaporationor application. When evaporation is chosen, for example, a film formingchamber is vacuum-exhausted until the degree of vacuum reaches 5×10⁻³Torr (0.665 Pa) or less, preferably 10⁻⁴ to 10⁻⁶ Pa, for evaporation.Prior to evaporation, the organic compound is vaporized by resistanceheating. The vaporized organic compound flies out to the substrate asthe shutter is opened for evaporation. The vaporized organic compoundflies upward and then deposits on the substrate through an openingformed in a metal mask. Layers of the organic compound-containing layerare formed by evaporation so that the light emitting element as a wholeemits white light.

For instance, an Alq₃ film, an Alq₃ film partially doped with Nile redwhich is a red light emitting pigment, an Alq₃ film, a p-EtTAZ film, anda TPD (aromatic diamine) film are layered in this order to obtain whitelight.

On the other hand, when the organic-compound containing layer is formedby application using spin coating, the layer after application ispreferably baked by vacuum heating. For example, an aqueous solution ofpoly(ethylene dioxythiophene)/poly(styrene sulfonic acid) (PEDOT/PSS) isapplied to the entire surface and baked to form a film that works as ahole injection layer. Then, a polyvinyl carbazole (PVK) solution dopedwith a luminescence center pigment (such as1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1),Nile red, or coumarin 6) is applied to the entire surface and baked toform a film that works as a light emitting layer.

Although the organic compound layer is a laminate in the above example,a single-layer film may be used as the organic compound layer. Forinstance, a 1,3,4-oxadiazole derivative (PBD) capable of transportingelectrons is dispersed in polyvinyl carbazole (PVK) capable oftransporting holes. Another method to obtain white light emission is todisperse 30 wt % of PBD as an electron transporting agent and dispersefour kinds of pigments (TPB, coumarin 6, DCM1, and Nile red) inappropriate amounts. Also, the organic compound layer may be a laminateof layers of high molecular weight material and layers of low molecularweight materials.

The next step is to form a thin film containing a metal of smallfunction (a film of an alloy such as MgAg, MgIn, AlLi, CaF₂, or CaN, ora film formed by co-evaporation of an element belonging to Group 1 or 2in the periodic table and aluminum) and to form a thin conductive film(an aluminum film here) 39 thereon by evaporation (FIG. 2B). An aluminumfilm is highly capable of blocking moisture and oxygen and therefore isa preferable material of the conductive film 39 for improvement of thereliability of the light emitting device. FIG. 2B is a sectional viewtaken along the dot-dash line A–A′ in FIG. 2A. This laminate is thinenough to let emitted light pass and functions as the cathode in thisembodiment. The thin conductive film may be replaced by a transparentconductive film (such as an ITO (indium oxide-tin oxide alloy) film, anIn₂O₃—ZnO (indium oxide-zing oxide alloy) film, or a ZnO (zinc oxide)film). On the conductive film 39, an auxiliary electrode may be formedin order to lower the resistance of the cathode. The cathode is formedselectively by resistance heating through evaporation using anevaporation mask.

The thus obtained light emitting element emits white light in thedirection indicated by the arrow in FIG. 2B. Light emitted in thelateral direction is reflected by the slope in the layer 36 c of thefirst electrode, thereby increasing the amount of light emitted in thearrow direction.

After the manufacturing process is thus finished up through formation ofthe second electrode (conductive film 39), the light emitting elementformed on the substrate 30 is sealed by bonding a sealing substrate(transparent substrate) using a seal agent. Spacers formed from a resinfilm may be provided in order to keep the gap between the sealingsubstrate and the light emitting element. The space surrounded by theseal agent is filled with nitrogen or other inert gas. For the sealagent, an epoxy-based resin is preferred. Desirably, the material of theseal agent transmits as little moisture and oxygen as possible. Asubstance having an effect of absorbing oxygen and moisture (e.g.,drying agent) may be placed in the space surrounded by the seal agent.

By enclosing the light emitting element in a space as above, the lightemitting element can be completely cut off from the outside and externalsubstances that accelerate degradation of the organic compound layer,such as moisture and oxygen, can be prevented from entering the lightemitting element. Accordingly, a highly reliable light emitting deviceis obtained.

Embodiment 2

This embodiment describes with reference to FIGS. 6A to 8 an example ofa light emitting device in which an auxiliary electrode is formed.

FIG. 6A is a top view of a pixel and a sectional view taken along thedot-dash line A–A′ is FIG. 6B.

In this embodiment, steps up through formation of an insulator 67 areidentical with those in Embodiment 1 and descriptions thereof areomitted here. The insulator 37 in FIG. 2B corresponds to the insulator67 in FIG. 6B.

Following the descriptions in Embodiment 1, a base insulating film, adrain region 62, a gate insulating film 63, an interlayer insulatingfilm 65, layers 66 a to 66 d of a first electrode, and the insulator 67are formed on a substrate having an insulating surface.

Next, an organic compound-containing layer 68 is selectively formed.This embodiment employs evaporation using an evaporation mask or ink jetto selectively form the organic compound-containing layer 68.

Then, an auxiliary electrode 60 is selectively formed on the insulator67 by evaporation using an evaporation mask. The thickness of theauxiliary electrode 60 is set to 0.2 to 0.5 μm. In the example given inthis embodiment, the auxiliary electrode 60 is placed in the direction Yas shown in FIG. 6A. However, arrangement of the auxiliary electrode isnot particularly limited and, as shown in FIG. 7, an auxiliary electrode70 placed in the direction X may be employed. A sectional view takenalong the dot-dash line A–A′ in FIG. 7 is identical with FIG. 2B.

FIG. 8 is an exterior diagram of the panel shown in FIG. 7. Theauxiliary electrode (auxiliary wire) 70 is led out as shown in FIG. 8and comes into contact with a lead-out wire 87 in a region between apixel portion 82 and a source side driving circuit 83. In FIG. 8,reference symbol 82 denotes the pixel portion, 83, the source sidedriving circuit, 84 and 85, gate side driving circuits, and 86, a powersupplying line. The wires that are formed at the same time the firstelectrode is formed are the power supplying line 86, the lead-out wire87, and a source wire. In FIG. 8, a terminal electrode for connectingwith an FPC is formed at the same time a gate wire is formed.

Similarly to Embodiment 1, the next step is to form a thin filmcontaining a metal of small function (a film of an alloy such as MgAg,MgIn, AlLi, CaF₂, or CaN, or a film formed by co-evaporation of anelement belonging to Group 1 or 2 in the periodic table and aluminum)and to form a thin conductive film (an aluminum film here) 69 thereon byevaporation. This laminate is thin enough to let emitted light pass andfunctions as the cathode in this embodiment. The thin conductive filmmay be replaced by a transparent conductive film (such as an ITO (indiumoxide-tin oxide alloy) film, an In₂O₃—ZnO (indium oxide-zing oxidealloy) film, or a ZnO (zinc oxide) film). In this embodiment, theauxiliary electrode 60 is formed on the insulator 67 such that theauxiliary electrode 60 comes into contact with the conductive film 69 inorder to lower the resistance of the cathode.

The thus obtained light emitting element emits white light in thedirection indicated by the arrow in FIG. 6B. Light emitted in thelateral direction is reflected by the slope in the layer 66 c of thefirst electrode, thereby increasing the amount of light emitted in thearrow direction.

This embodiment is also applicable to a light emitting device having alarge-sized pixel portion since the resistance of the cathode is loweredby forming the auxiliary electrode 60 or 70.

In the example shown in this embodiment, the auxiliary electrode 60 isformed after the organic compound-containing layer 68 is formed.However, in what order they are formed is not particularly limited andthe organic compound-containing layer may be formed after the auxiliaryelectrode 60 is formed.

This embodiment can be combined freely with any one of Embodiment Modes1 through 3 and Embodiment 1.

Embodiment 3

Further, an exterior view of an active matrix type light emittingapparatus is described with reference to FIG. 9. Further, FIG. 9A is atop view showing the light emitting apparatus and FIG. 9B is across-sectional view of FIG. 9A taken along a line A–A′. Referencenumeral 901 indicated by a dotted line designates a source signal linedriver circuit, numeral 902 designates a pixel portion, and numeral 903designates a gate signal line driver circuit. Further, numeral 904designates a seal substrate, numeral 905 designates a seal agent and aninner side surrounded by the seal agent 905 constitutes a space 907.

Further, reference numeral 908 designates a wiring for transmittingsignals inputted to the source signal line driver circuit 901 and thegate signal line driver circuit 903 for receiving a video signal or aclock signal from FPC (flexible printed circuit) 909 for constituting anexternal input terminal. Further, although only FPC is illustrated here,the FPC may be attached with a printed wiring board (PWB). The lightemitting apparatus in the specification includes not only a main body ofthe light emitting apparatus but also a state in which FPC or PWB isattached thereto.

Next, a sectional structure will be explained in reference to FIG. 9B.Driver circuits and the pixel portion are formed over a substrate 910and here, the source signal line driver circuit 901 as the drivercircuit and the pixel portion 902 are shown.

Further, the source signal line driver circuit 901 is formed with a CMOScircuit combined with an n-channel type TFT 923 and a p-channel type TFT924. Further, TFT for forming the driver circuit may be formed by apublicly known CMOS circuit, PMOS circuit or NMOS circuit. Further,although according to the embodiment, a driver integrated type formedwith the driver circuits over the substrate is shown, the driverintegrated type is not necessarily be needed and the driver circuits canbe formed not over the substrate but at outside thereof.

Further, the pixel portion 902 is formed by a plurality of pixels eachincluding a switching TFT 911 and a first electrode (anode) 913electrically connected to a drain thereof.

Further, an insulating layer 914 is formed at both ends of the firstelectrode (anode) 913, a portion of the first electrode forms a slopealong a side of the insulating layer 914. The slope of the firstelectrode is formed at the same time of a formation of the insulatinglayer 914. Light generated at a layer containing organic compound 915 isreflected by the slope in order to increase an amount of luminescence inthe direction indicated by an arrow in FIG. 9.

The layer containing an organic compound 915 is selectively formed onthe first electrode (anode) 913. Further, a second electrode (cathode)916 is formed over the organic compound layer 915. Thereby, a lightemitting element 918 comprising the first electrode (anode) 912, theorganic compound layer 915 and the second electrode (cathode) 916 isformed. Here, the light emitting element 918 shows an example of whitecolor luminescence and therefore, provided with the color filtercomprising a coloring layer 931 and BM932 (for simplification, overcoatlayer is not illustrated here).

A third electrode (an auxiliary electrode) 917 which is a part of astructure shown in Embodiment 2 is formed on the insulating layer 914 torealize that the second electrode has a lower resistance. The secondelectrode (cathode) 916 functions also as a wiring common to all thepixels and electrically connected to FPC 909 via the third electrode 917and the connection wiring 908.

Further, in order to seal the light emitting element 918 formed over thesubstrate 910, the seal substrate 904 is pasted by the seal agent 905.Further, a spacer comprising a resin film may be provided for ensuringan interval between the seal substrate 904 and the light emittingelement 918. Further, the space 907 on the inner side of the seal agent905 is filled with an inert gas of nitrogen or the like. Further, it ispreferable to use epoxy species resin for the seal agent 905. Further,it is preferable that the seal agent 905 is a material for permeatingmoisture or oxygen as less as possible. Further, the inner portion ofthe space 907 may be included with the substance having an effect ofabsorbing oxygen of water.

Further, according to this embodiment, as a material for constitutingthe seal substrate 904, other than glass substrate or quartz substrate,a plastic substrate comprising FRP (Fiberglass-Reinforced Plastics), PVF(polyvinyl fluoride), Mylar, polyester or acrylic resin can be used.Further, it is possible to adhere the seal substrate 904 by using theseal agent 905 and thereafter seal to cover a side face (exposed face)by a seal agent.

By sealing the light emitting element in the space 907 as describedabove, the light emitting element can completely be blocked from outsideand a substance for expediting to deteriorate the organic compound layersuch as moisture or oxygen can be prevented from invading from outside.Therefore, the highly reliable light emitting apparatus can be provided.

Further, this embodiment can freely be combined with Embodiment Modes 1to 3, and Embodiments 1, 2.

Embodiment 4

By implementing the present invention, all of electronic apparatusintegrated with a module having an organic light emitting element(active matrix type EL module) are completed.

As such electronic apparatus, a video camera, a digital camera, a headmount display (goggle type display), a car navigation apparatus, aprojector, a car stereo, a personal computer, a portable informationterminal (mobile computer, portable telephone or electronic book) andthe like are pointed out. FIGS. 10 and 11 show examples of these.

FIG. 10A is a personal computer which includes a main body 2001, animage input portion 2002, a display portion 2003 and a keyboard 2004.

FIG. 10B is a video camera which includes a main body 2101, a displayportion 2102, a voice input portion 2103, an operation switch 2104, abattery 2105, an image receiving portion 2106.

FIG. 10C is a mobile computer which includes a main body 2201, a cameraportion 2202, an image receiving portion 2203, an operation switch 2204and a display portion 2205.

FIG. 10D is a goggle type display which includes a main body 2301, adisplay portion 2302 and an arm portion 2303.

FIG. 10E is a player using a record medium recorded with programs(hereinafter, referred to as record medium) which includes a main body2401, a display portion 2402, a speaker portion 2403, a record medium2404 and an operation switch 2405. Further, the player uses DVD (DigitalVersatile Disc) or CD as a record medium and can enjoy music, enjoymovie and carry out the game or Internet.

FIG. 10F is a digital camera which includes a main body 2501, a displayportion 2502, an eye-piece portion 2503, an operation switch 2504 and animage receiving portion (not illustrated).

FIG. 11A is a portable telephone which includes a main body 2901, avoice output portion 2902, a voice input portion 2903, a display portion2904, an operation switch 2905, an antenna 2906 and an image inputportion (CCD, image sensor) 2907.

FIG. 11B is a portable book (electronic book) which includes a main body3001, display portions 3002, 3003, a record medium 3004, an operationswitch 3005, an antenna 3006.

FIG. 11C is the display which includes a main body 3101, a support base3102 and a display portion 3103.

Incidentally, the display shown in FIG. 11C is of a screen size ofmiddle or small type or large type, for example, a screen size of 5 to20 inches. Further, in order to form the display portion of this size,it is preferable to use a display portion having a side of a substrateof 1 m and carry out mass production by taking many faces. In case thatthe screen having a size of middle or small type or large type isformed, it is preferable that the auxiliary electrode shown inEmbodiment 2 or Embodiment 3 is formed.

As described above, a range of applying the invention is extremely wideand is applicable to a method of fabricating electronic apparatus of allthe fields. Further, the electronic apparatus of the embodiment can berealized by using a constitution comprising any combination ofEmbodiment Modes 1 to 3 and Embodiments 1 to 3.

According to the present invention, a portion of light emitted from anorganic compound-containing layer that is emitted in the lateraldirection (the direction parallel to the substrate face) is reflected bya slope formed in a stepped portion of a first electrode to therebyincrease the total amount of light taken out in a certain direction (adirection in which light passes the second electrode). In short, a lightemitting device with less stray light and other types of light emissionloss can be obtained.

Furthermore, the structure of the present invention requires fewer masksin total in its manufacture process.

1. A light emitting device comprising: a first electrode connected to athin film transistor over a substrate having an insulating surface; aninsulator over and covering an edge portion of the first electrode; alayer containing an organic compound formed over the first electrode;and a second electrode over the layer containing the organic compound,wherein the first electrode has a depression having a sloped surface,and the first electrode in the center of the depression is thinner thanthe first electrode in the edge of the depression, wherein the layercontaining the organic compound is in contact with the sloped surface,and wherein the first electrode comprises titanium.
 2. A light emittingdevice according to claim 1, wherein the second electrode is atransmissive conductive film.
 3. A light emitting device according toclaim 1, wherein the depression is formed in a self-aligning mannerusing the insulator as a mask.
 4. A light emitting device according toclaim 1, wherein the first electrode is an anode and the secondelectrode is a cathode.
 5. A light emitting device according to claim 1,wherein the first electrode is a cathode and the second electrode is ananode.
 6. A light emitting device according to claim 1, wherein theangle of inclination of the sloped surface is more than 30° and lessthan 70°.
 7. A light emitting device according to claim 1, wherein anupper edge portion of the insulator for covering the edge portion of thefirst electrode is curved to have a radius of curvature and the radiusof curvature is set to 0.2 to 3 μm.
 8. A light emitting device accordingto claim 1, wherein the layer containing the organic compound is made ofa material emitting red light, green light, or blue light.
 9. A lightemitting device according to claim 1, wherein the layer containing theorganic compound is made of a material emitting white light, and iscombined with a color filter provided in a sealing member.
 10. A lightemitting device according to claim 1, wherein the layer containing theorganic compound is made of a material emitting monochromatic light, andis combined with one of a color conversion layer and a colored layerprovided in a sealing member.
 11. A light emitting element according toclaim 1, wherein the light emitting device is any one of a video camera,a digital camera, a goggle-type display, a car navigation system, apersonal computer, a DVD player, an electronic game machine, and aportable information terminal.
 12. A light emitting device according toclaim 1, wherein the first electrode is directly connected to the thinfilm transistor.
 13. A light emitting device comprising: a firstelectrode connected to a thin film transistor over a substrate having aninsulating surface; an insulator over and cover covering an edge portionof the first electrode; a layer containing an organic compound formedover a first electrode; and a second electrode over the layer containingthe organic compound, wherein the first electrode has a depressionhaving a sloped surface, and the first electrode in the center of thedepression is thinner than the first electrode in the edge of thedepression, and wherein the layer containing the organic compound is incontact with the sloped surface.
 14. A light emitting device accordingto claim 13, wherein the second electrode is a transmissive conductivefilm.
 15. A light emitting device according to claim 13, wherein thedepression is formed in a self-aligning manner using the insulator as amask.
 16. A light emitting device according to claim 13, wherein thefirst electrode is an anode and the second electrode is a cathode.
 17. Alight emitting device according to claim 13, wherein the first electrodeis a cathode and the second electrode is an anode.
 18. A light emittingdevice according to claim 13, wherein the angle of inclination of thesloped surface is more than 30° and less than 70°.
 19. A light emittingdevice to claim 13, wherein an upper edge portion of the insulator forcovering the edge portion of the first electrode is curved to have aradius of curvature and the radius of curvature is set to 0.2 to 3 μm.20. A light emitting device according to claim 13, wherein the layercontaining the organic compound is made of a material emitting redlight, green light, or blue light.
 21. A light emitting device accordingto claim 13, wherein the layer containing the organic compound is madeof a material emitting white light, and is combined with a color filterprovided in a sealing member.
 22. A light emitting device according toclaim 13, wherein the layer containing the organic compound is made of amaterial emitting monochromatic light, and is combined with one of acolor conversion layer and a colored layer provided in a sealing member.23. A light emitting element according to claim 13, wherein the lightemitting device is any one of a video camera, a digital camera, agoggle-type display, a car navigation system, a personal computer, a DVDplayer, an electronic game machine, and a portable information terminal.24. A light emitting device according to claim 13, wherein the firstelectrode is directly connected to the thin film transistor.
 25. A lightemitting device comprising: a first electrode connected to a thin filmtransistor over a substrate having an insulating surface; an insulatorover and covering and edge portion of the first electrode; a layercontaining an organic compound formed over the first electrode; and asecond electrode over the layer, wherein the first electrode has amulti-layer structure, wherein the first electrode has a depressionhaving a sloped surface, wherein the number of layers of the multi-layerstructure in the depression is smaller than the number of layers of themulti-layer structure outside the depression, and wherein the layercontaining the organic compound is in contact with the sloped surface.26. A light emitting device according to claim 25, wherein the secondelectrode is a transmissive conductive film.
 27. A light emission deviceaccording to claim 25, wherein the depression is formed in aself-aligning manner using the insulator as a mask.
 28. A light emittingdevice according to claim 25, wherein the first electrode is an anodeand the second electrode is a cathode.
 29. A light emitting deviceaccording to claim 25, wherein the first electrode is a cathode and thesecond electrode is an anode.
 30. A light emitting device according toclaim 25, wherein the angle of inclination of the sloped surface is morethan 30° and less than 70°.
 31. A light emitting device according toclaim 25, wherein an upper edge portion of the insulator for coveringthe edge portion of the first electrode is curved to have a radius ofcurvature and the radius of curvature is set to 0.2 to 3 μm.
 32. A lightemitting device according to claim 25, wherein the layer containing theorganic compound is made of a material emitting red light, green light,or blue light.
 33. A light emitting device according to claim 25,wherein the layer containing the organic compound is made of a materialemitting white light, and is combined with a color filter provided in asealing member.
 34. A light emitting device according to claim 25,wherein the layer containing the organic compound is made of a materialemitting monochromatic light, and is combined with one of a colorconversion layer and a colored layer provided in a sealing member.
 35. Alight emitting element according to claim 25, wherein the light emittingdevice is any one of a video camera, a digital camera, a goggle-typedisplay, a car navigation system, a personal computer, a DVD player, anelectronic game machine, and a portable information terminal.
 36. Alight emitting device according to claim 25, wherein the first electrodeis directly connected to the thin film transistor.
 37. A light emittingdevice comprising: a first electrode connected to a thin film transistorover a substrate having an insulating surface; an insulator over andcovering an edge portion of the first electrode; a layer comprsing anorganic compound formed over the first electrode; and a second electrodeover the layer; wherein the first electrode has a multi-layer structure,wherein the first electrode has a depression having a sloped surface,wherein the number of layers of the multi-layer structure in thedepression is smaller than the number of layers of the multi-layerstructure outside the depression, wherein the layer containing theorganic compound is in contact with the sloped surface, and wherein thefirst electrode comprises titanium.
 38. A light emitting deviceaccording to claim 37, wherein the second electrode is a transmissiveconductive film.
 39. A light emitting device according to claim 37,wherein the angle of inclination of the sloped surface is more than 30°and less than 70°.
 40. A light emitting device according to claim 37,wherein the layer containing the organic compound is made of a materialemitting red light, green light, or blue light.
 41. A light emittingdevice according to claim 37, wherein the first electrode is directlyconnected to the thin film transistor.